4.3 jelly bean is last for current devices?

Hi, it's just an idea I literally had now. I was wondering if 4.3 will be the last update for any current devices released before 5.0 KLP? Because Microsoft did that with wp7.8, instead of updating devices to wp8 because it had a new kernel core or something. I was wondering if KLP was such a big change that it had a new kernel so it wouldn't be on current devices, and that's why they won't be showing it at I/O???? Anyway, just an idea. It might put an end to fragmentation if they start again also.